It is known to measure the loading in the drives or gearing of known installations with the aid of measuring devices embodied as pins incorporating strain gauge sensors. The signals generated by the sensors are then used to monitor loading and can trigger an overload de-coupling means if the measured load rises above some threshold. Known types of measuring devices are described in U.S. Pat. Nos. 4,614,134 and 4,601,218.
In the case of chain driven ploughs it is necessary to pre-tension the endless drive chain to avoid harmful slackness and whipping on the one hand and to avoid excessive tension which increases wear. To obtain the right degree of pre-tension it is known to have a chain wheel which is displaced with a piston and cylinder unit. There is a need for a simple arrangement which is able to measure chain tension with sufficient accuracy to enable the pre-tensioning to be optimised and the dynamic tension to be monitored continuously. In one known arrangement, described in U.S. Pat. No. 5,037,315, the chain wheel is supported by a shaft in bearings in a housing for gearing driving the shaft. One bearing is fixed while the other is displaceable and bears on a ring which engages on force measuring devices with strain gauge sensors. There is a need for a simple yet reliable alternative to the use of a displaceable bearing.
An object of the invention is to provide an arrangement which is easy to fit and maintain without extensive modification yet enables an accurate measurement of chain tension.